kernel: mem_domain: keep track of threads only if needed

arch/Kconfig

@@ -57,6 +57,7 @@ config ARM64
 	select ARCH_HAS_DEMAND_MAPPING
 	select ARCH_SUPPORTS_EVICTION_TRACKING
 	select EVICTION_TRACKING if DEMAND_PAGING
+	select MEM_DOMAIN_HAS_THREAD_LIST if ARM_MPU
 	help
 	  ARM64 (AArch64) architecture
 

arch/arm64/core/cortex_r/arm_mpu.c

@@ -760,8 +760,8 @@ static int configure_domain_partitions(struct k_mem_domain *domain)
 	struct k_thread *thread;
 	int ret;
 
-	SYS_DLIST_FOR_EACH_CONTAINER(&domain->mem_domain_q, thread,
-				     mem_domain_info.mem_domain_q_node) {
+	SYS_DLIST_FOR_EACH_CONTAINER(&domain->thread_mem_domain_list, thread,
+				     mem_domain_info.thread_mem_domain_node) {
 		ret = configure_dynamic_mpu_regions(thread);
 		if (ret != 0) {
 			return ret;

include/zephyr/app_memory/mem_domain.h

@@ -83,8 +83,13 @@ struct k_mem_domain {
 #endif /* CONFIG_ARCH_MEM_DOMAIN_DATA */
 	/** partitions in the domain */
 	struct k_mem_partition partitions[CONFIG_MAX_DOMAIN_PARTITIONS];
-	/** Doubly linked list of member threads */
-	sys_dlist_t mem_domain_q;
+#ifdef CONFIG_MEM_DOMAIN_HAS_THREAD_LIST
+	/** Doubly linked list of member threads,
+	 * pointer to the thread_mem_domain_node inside
+	 * each thread's memory domain info struct.
+	 */
+	sys_dlist_t thread_mem_domain_list;
+#endif /* CONFIG_MEM_DOMAIN_HAS_THREAD_LIST */
 	/** number of active partitions in the domain */
 	uint8_t num_partitions;
 };

include/zephyr/kernel/thread.h

@@ -178,8 +178,10 @@ typedef struct _thread_stack_info _thread_stack_info_t;
 
 #if defined(CONFIG_USERSPACE)
 struct _mem_domain_info {
+#ifdef CONFIG_MEM_DOMAIN_HAS_THREAD_LIST
 	/** memory domain queue node */
-	sys_dnode_t mem_domain_q_node;
+	sys_dnode_t thread_mem_domain_node;
+#endif /* CONFIG_MEM_DOMAIN_HAS_THREAD_LIST */
 	/** memory domain of the thread */
 	struct k_mem_domain *mem_domain;
 };

kernel/Kconfig.mem_domain

@@ -76,4 +76,13 @@ config MEM_DOMAIN_ISOLATED_STACKS
 	  Regardless of this settings, threads cannot access the stacks of
 	  threads outside of their domains.
 
+config MEM_DOMAIN_HAS_THREAD_LIST
+	bool
+	help
+	  If enabled, there is a doubly linked list in each memory domain
+	  struct to keep track of the threads associated with this
+	  particular memory domain.
+
+	  This is selected by architecture needing this to function.
+
 endmenu

kernel/mem_domain.c

@@ -113,7 +113,10 @@ int k_mem_domain_init(struct k_mem_domain *domain, uint8_t num_parts,
 
 	domain->num_partitions = 0U;
 	(void)memset(domain->partitions, 0, sizeof(domain->partitions));
-	sys_dlist_init(&domain->mem_domain_q);
+
+#ifdef CONFIG_MEM_DOMAIN_HAS_THREAD_LIST
+	sys_dlist_init(&domain->thread_mem_domain_list);
+#endif /* CONFIG_MEM_DOMAIN_HAS_THREAD_LIST */
 
 #ifdef CONFIG_ARCH_MEM_DOMAIN_DATA
 	ret = arch_mem_domain_init(domain);
@@ -265,8 +268,12 @@ static int add_thread_locked(struct k_mem_domain *domain,
 	__ASSERT_NO_MSG(thread != NULL);
 
 	LOG_DBG("add thread %p to domain %p\n", thread, domain);
-	sys_dlist_append(&domain->mem_domain_q,
-			 &thread->mem_domain_info.mem_domain_q_node);
+
+#ifdef CONFIG_MEM_DOMAIN_HAS_THREAD_LIST
+	sys_dlist_append(&domain->thread_mem_domain_list,
+			 &thread->mem_domain_info.thread_mem_domain_node);
+#endif /* CONFIG_MEM_DOMAIN_HAS_THREAD_LIST */
+
 	thread->mem_domain_info.mem_domain = domain;
 
 #ifdef CONFIG_ARCH_MEM_DOMAIN_SYNCHRONOUS_API
@@ -283,7 +290,10 @@ static int remove_thread_locked(struct k_thread *thread)
 	__ASSERT_NO_MSG(thread != NULL);
 	LOG_DBG("remove thread %p from memory domain %p\n",
 		thread, thread->mem_domain_info.mem_domain);
-	sys_dlist_remove(&thread->mem_domain_info.mem_domain_q_node);
+
+#ifdef CONFIG_MEM_DOMAIN_HAS_THREAD_LIST
+	sys_dlist_remove(&thread->mem_domain_info.thread_mem_domain_node);
+#endif /* CONFIG_MEM_DOMAIN_HAS_THREAD_LIST */
 
 #ifdef CONFIG_ARCH_MEM_DOMAIN_SYNCHRONOUS_API
 	ret = arch_mem_domain_thread_remove(thread);